Tissue ( Epithelial Tissue ) | NEET BIOLOGY FAST REVISION

Structural Organization In Animals -  TISSUE

Tissue is group of cells that have a similar structure and act together to perform a specific function .

There are four different types tissues in animals : epithelial ( ectoderm , mesoderm , endoderm ) , connective ( mesoderm ) , muscular ( mesoderm) and nervous ( ectoderm ) tissue .

Tissues perform various functions like digestion , respiration , reproduction , etc.

The study of tissues is called histology ( Mayer , 1819 ).

EPITHELIAL TISSUE

An epithelium or epithelial tissue is composed of one or more layers of cells covering the external and internal surfaces of various body parts . Epithelial tissue also forms glands .

Epithelial membranes are derived from all three germ layers . The epidermis , derived from ectoderm , constitutes the outer portion of the skin while the inner surface of the digestive tract is lined by an epithelium derived from endoderm and the inner surfaces of the body cavities are lined by an epithelium derived from mesoderm.

Epithelial tissue usually rests on a thin non - cellular basement membrane composed of outer thin basal lamina consisting of mucopolysaccharides and glycoproteins and inner thick fibrous or reticular lamina consisting of collagen or reticular fibres of the underlying connective tissue.

These tissues generally lack blood vessels but still have a good power of repair after injury.

They receive useful materials from the blood vessels of the connective tissue through diffusion across the basement membrane and transfer waste matter to the blood in the same way .

There are five types of specialised junctions present between epithelial cells . They are tight junctions , gap junctions , adhering junctions , interdigitations and intercellular bridges .

Manish Mevada

M.Sc, M.Phil. B.Ed